Such seal assemblies have long been used in oil-film bearings. As a rule expensive seal elements are used which on the one hand prevent oil from getting from the oil-film bearing to the roll body and on the other hand prevent particle-carrying coolant and lubricant from getting from the roll body into the oil-film bearing.
As a result of the various loads encountered during rolling, the roll stub can get radially offset in its mount. In unloaded nonworking rolls the seal space between the roll-stub sleeve and the bearing sleeve is less in a lower region, whereas the gap is greater in the opposite upper region. If the roll is working and pressure is being exerted from the mount through the bearing to the roll, the bearing gap between the roll-stub sleeve and the bearing sleeve is greater in the lower region whereas in the opposite upper region it decreases. This radial offset created by different loads must be compensated out by the seal elements.
As a result when the roll is not under load the seal lips in the lower region of the seal element are pushed together, while the seal lips in the upper region barely touch the seal surface. When the roll is working the seal lips are on the contrary pushed together a great deal in the upper region of the seal element and in the lower region barely touch the seal surface.
This radial play therefore creates a considerable load and as a result wear of the seal on the one hand from being squeezed together and on the other hand from the constant load change and furthermore the danger that the sealing effectiveness is not optimal with respect to the seal surface engaged by the seal lips.